1. Field of Invention
The invention relates in general to a fingerprint sensing device, and more particularly to a fingerprint sensing device with a flexible printed circuit board and a method of manufacturing the same.
2. Related Art
Most non-optical fingerprint sensors are designed and formed on silicon chips or wafers. The basic structure of each of the capacitive, electric field, RF or thermal sensing chip or other sensing chips includes a sensing cell array, which is formed above the silicon chip and can be in direct contact with the finger to measure the finger ridge or the finger valley images. The technology associated with the fingerprint sensing chip may be found in the following patents proposed by the present inventor: (a) U.S. patent application Ser. No. 10/403,052, filed on Apr. 1, 2003, entitled “CAPACITIVE FINGERPRINT SENSOR”, and issued on Aug. 29, 2006 as U.S. Pat. No. 7,099,497; (b) U.S. patent application Ser. No. 10/434,833, filed on May 13, 2003, entitled “PRESSURE TYPE FINGERPRINT SENSOR FABRICATION METHOD”, and issued on Jul. 6, 2004 as U.S. Pat. No. 6,759,264; (c) U.S. patent application Ser. No. 10/414,214 (US20040208345A1), filed on Apr. 16, 2003, and entitled “THERMOELECTRIC SENSOR FOR FINGERPRINT THERMAL IMAGING”; (d) U.S. patent application Ser. No. 10/638,371 (US20040046574A1), filed on Aug. 12, 2003, and entitled “CAPACITIVE MICRO PRESSURE SENSING MEMBER AND FINGERPRINT SENSOR USING THE SAME”; and (e) Taiwan Patent Application No. 090112023, filed on May 17, 2001, and entitled “CAPACITIVE PRESSURE MICROSENSOR AND METHOD FOR MANUFACTURING THE SAME AND DETECTING SIGNALS OF THE SAME”, now published as TW541503 and issued as Invention Patent Number 182652.
For a complete sensor structure, an insulating layer to be in contact with the finger is always formed on a surface of the chip to prevent the surface of the chip from being worn out by the finger. Because the insulating layer of the fingerprint chip is usually formed by way of film deposition and most insulating layers are made of fragile dielectric materials, the insulating layer on the surface of the chip cannot withstand a large pressure or an impact of force. In addition, the insulating layer formed in the film manufacturing process is usually too thin to achieve a long-term, good wearing resistance.
Furthermore, when the object with the electrostatic charges approaches to the chip, the electrostatic charges may be discharged through the surface of the chip and thus the chip may be damaged. The reason is that the insulating layer is too thin so that the ability of the chip for withstanding the electrostatic charge damage is restricted.
Thus, it is an important subject of the invention to provide a fingerprint sensing chip capable of withstanding the pressure, force impact, wearing and the electrostatic charge damage, and a method of manufacturing the same so that the problems in the related art can be solved.